Plug-in cap with ground indicating light



Aug- 2. 1961 R. J. COSTANZO 2,997,701

PLUG-IN CAP WITH GROUND INDICATING LIGHT Filed Oct. 16, 1958 2Sheets-Sheet 1 INVENTOR W1 ATTO RN EYS R. J. COSTANZO PLUG-IN CAP WITHGROUND INDICATING LIGHT Filed 001;. 16, 1958' Aug. 22, 1961 2Sheets-Sheet 2 '3 M Z? B/ack 6 f II M/ '7 l J f/vfc i l Z? 4 I l 7 KY} W5/ af w a if? Green 3 LL-I Fig. 6.

INVENTOR ATTORNEY5 United States Patent 2,997,701 PLUG-IN CAPWITIIIIEROUND INDICATING HT Raphael J. Costanzo, Bridgeport, Conn.,assignor to Harvey Hubbell, Incorporated, Bridgeport, Conn., acorporation of Connecticut Filed Oct. 16, 1958, Ser. No. 767,704 4Claims. (Cl. 340-255) This invention relates to a plug-in cap withground indicating light, and has for an object to provide such a capwith simple and eifective means such as a signal or indicating light soconnected that when used for supplying electric current to a groundedelectrical power device or attachment, this light will indicate whetherthe ground is working and in good condition, or whether it has beenbroken.

Another object is to provide such a device that merely plugging the capinto an outlet receptacle for supplying current to the electrical devicewill, through this indicating light, show whether the ground from theelectrical device or attachment is in good condition and functioningproperly.

With the foregoing and other objects in view, I have devised theconstruction illustrated in the accompanying drawing forming a part ofthis specification. It is, however, to be understood the invention isnot limited to the specific details of construction and arrangementshown, but may embody various changes and modifications within the scopeof the invention.

In these drawings:

FIG. 1 is a top view of the lower member of the cap with certain partsin section and the fuses removed, the section being substantially online 1-1 of FIG. 3;

FIG. 2 is a similar view looking toward the bottom of the upper sectiontaken substantially on line 22 of FIG. 3, and with parts broken away tomore clearly show the construction;

FIG. 3 is a longitudinal section of the complete plug-in cap takensubstantially on line 3-3 of FIG. 2;

FIG. 4 is a bottom or end view looking toward the bottom of FIG. 3;

FIG. 5 is a diagrammatical view showing the various elements on the plugand electrical connections to an electric attachment or power device,such, for example, as an electric hand drill, and

FIG. 6 is a wiring diagram of the connections involved.

The cap 10 is the regular fused and grounded cap used for plugging intoan outlet receptacle or similar connection (not shown) for supplyingcurrent to some electrical attachment or power-operated device such, forexample, as a motor 11 in a hand drill or similar device, including agrounded frame or casing 12. This cap is provided with means to indicatewhether the ground connection from this casing or frame 12, for example,of the motor, is as it should be and functioning properly, or whether ithas been broken. This plug-in cap comprises a body including two bodysections of insulating material indicated at 13 and 14, and foridentification purposes the member 13 will be called the upper memberand member 14 the lower member. Mounted in the lower member in a recessor chamber 15 in the inner or top wall thereof are connections formounting the contacts 16, 17 and 18, one of which (18) is the groundingcontact, and 16 may be indicated as the hot contact and 17 the return orneutral wire of the power circuit. The contacts 16 and 17 extend throughslots 19 and 20 in the end wall of the member 14 where they terminate inlateral plates or connectors 22 respectively mounted on the bottom ofthe recess 15 by any suitable means such, for example, as screws 23threaded through the plates 22 into the material of the body or intothreaded inserts molded in this body, or they could be permanentlyconnected by riveted-over inserts. The contacts 16, 17 and 18 aretransversely curved and have a wider overhanging end portion 24 at theirfree ends providing a locking shoulder 25 adapted to lock with shouldersin the body of the receptacle into which they may be inserted, by alimited relative turning movement after they are so inserted in thereceptacle. Mounted on each of the base connectors 22 is a spring clip26 which may be used for holding one end of a fuse cartridge 27 andforms electrical connection from the end contact 28 thereof to thecontacts 16 and 17.

Mounting and gripping the other ends of the fuse cartridges 27 aresimilar spring contacts 29 mounted on the conductor bars or plates 30and 31 mounted in the recess 32 in the inner or bottom wall of the bodymember 13 by any suitable means, such, for example, as screws 33 and 34which may also be binding screws for connecting lead wires to theconductors 30 and 31. The body 13 is provided with a passage 35 leadingfrom the top wall thereof to the recess 32 to which conductor wires ofan insulating electric cable may be led for connection t0 the variouselements in the cap. In the arrangement shown a hot or black wire 36 isconnected to the conductor 30 by the binding screw 33 and through a fuse27 to the contact 16. Similarly, the return or neutral white wire 37 isconnected to the conductor 31 by the binding post 33 and through asimilar fuse 27 to the contact 17. The green or ground wire 38 isconnected by a binding screw 39 to a plate 40 mounted in the bottomrecess 15 in the lower body member and electrically connected by a screw41 to the base 42 of the grounding contact 18, this base being locatedin a recess in the lower end wall of the member 14. This screw 41 andsimilar screw 43 are passed through the lower member 14 and threadedinto an insert (not shown) in the upper member 13 to connect these twomembers together after the various elements have been assembled.

Mounted in the side wall of the body member 13 is an indicating light 44which may be a neon glow light, and it is mounted in a recess 45 in aside wall of the member 13, which recess opens through the outer surfaceof this member. One contact of this light, indicated at 46, is connectedthrough a resistor 47 to the conductor 30, as indicated at 48, and theother lead or conductor 49 from this lamp is connected to a bindingscrew 50 to a conductor 51 in the cable, which is indicated as a redconductor, and it is connected at the other end of the cable to theframe or casing 12 of the motor or electrical device to be operated, asshown in FIGS. 5 and 6. The hot or black wire 36 and the white or returnwire 37 are connected to the motor 11 for supplying power to this motor.The frame or casing 12 of the motor is grounded through the green wire38, which is connected to this casing at one end, as shown at 38a, andleads to the grounded contact 18 in the cap. The indicating lamp 44 maybe covered and protected in its recess 45 by a transparent protectivecap 52 which may be screwed into or forced or snapped into a recess 53at the outer end of the recess 55 or cemented in position.

In operation, as shown in FIGS. 5 and 6, plugging this cap into thegrounded outlet receptacle or connector will connect the hot contact 16to the hot side of the power circuit, the contact 17 connected to thereturn and 18 connected to the grounded contact in the receptacle. Itsground is indicated at 54. If the grounded connection 38 from the motorframe or casing 12 is in proper working order, current will flow fromcontact 16 through the resistor 47 to the light 44 and through the redconnection 51 to the frame or casing 12 and back through the greenconnection 38 from this casing to the grounded contact 18. Thus the lamp47 will glow and indicate that the grounding connection is intact andworking properly. The resistor 47 has sufficiently high resistance toprotect the lamp 44 and supply proper small current for operation ofthis lamp. Should the grounding connection 38 from the frame or casingof the motor be broken or not functioning properly, then the lamp willnot glow, and will indicate immediately to the operator either that theground connection is broken or not functioning, and will warn him forsafetys sake to see that the proper ground from the motor casing isrestored before the motor and the electrical device is operated. The twofuses 27 may or may not be used, and if not used the loads 36 and 37 maybe connected directly to the contacts 16 and 17 respectively.

It will be seen from the above that this provides a very simple andeffective device which will function from the mere act of inserting theblades of the plug-in cap into the outlet receptacle or otherconnection, to indicate immediately to the operator whether the groundfrom the frame or casing of the motor to be operated by power from thisreceptacle is functioning properly, or should be restored before use ofthe motor or use of the device operated by it.

Having thus set forth the nature of my invention, I claim:

1. A plug-in cap comprising a body of insulating ma terial, bladecontacts projecting therefrom for insertion in an outlet receptacle andincluding power circuit contacts and a grounding contact, an indicatinglight mounted in the body, conductor wires connected to the contacts andextending from the body with the wires from the power contacts adaptedfor connection to a motor of an electrical device to supply powerthereto and the wire from the grounding contact adapted for connectionto the casing of the motor to ground it, a resistor in the bodyconnected in series with one of the power contacts and the light, and aconductor wire connected to the light and extending from the body so asto be adapted to be connected to the casing of the motor to ground thelight through the first ground connection.

2. A plug-in cap comprising a body, blade contacts projecting from thesaid body for insertion in an outlet receptacle including power circuitcontacts and a ground ing contact, said body provided with a recessopening through one side thereof, an indicating light mounted in saidrecess, conductor wires connected with the contacts and extending fromthe body where they are adapted for connection to the motor of anelectrical device to supply current to the motor and to ground itscasing, a resistor in the body, conductor means connecting the resistorin series with one of the power contacts and one side of the light, anda conductor wire connected to the other side of the light and extendingfrom the body adapted for connection to the motor casing to ground thelight thereon.

3. In combination, a plug-in cap and an electric motor including acasing, said cap including a body, blade contacts projecting from thebody for insertion in an outlet receptacle, said contacts includingpower circuit contacts and a grounding contact, an indicating lightmounted in the body, conductor wires extending from the power circuitcontacts-to the motor to supply current thereto, a conductor wireextending from the grounding contact to the motor casing, a resistormounted in the body, and conductor means connecting the resistor andlight in series with one of the power circuit contacts and the motorcasing.

4. In combination, a plug-in cap and an electrically operated deviceincluding a motor and a casing, said cap comprising a body provided witha recess opening through one side thereof, blade contacts projectingfrom the body for insertion in an outlet receptacle and including powercircuit contacts and a grounding contact, an indicating light mounted insaid recess, a resistor mounted in the body, lead wires extending fromthe power circuit contacts to the motor for supplying current thereto, alead wire extending from the grounding contact to the motor casing, andconductor means connecting the resistor, the light and the motor casingin series with the hot side of the power circuit.

References Cited in the file of this patent UNITED STATES PATENTS

